The present invention relates to a durable water repellent agent capable of maintaining its effect over a prolonged period of time.
Water repellent compositions which form coating films on concrete, wood, cloth and other substrates to show the water repelling property and are useful in various fields have been widely used in the field of construction and building materials, for instance. Those organosilicon and like compounds have so far been used as such repellents, however, which cannot fully show their repellent property when pools of water stay on the substrate surface for long. In addition, they are poor in weather resistance.
Therefore, the use of fluorine-containing resins has been proposed. For example, Japanese Patent Publication Sho-62-16141 proposed that a coating composition comprising an epoxy resin and/or a phenol/alkyd resin or the like be used as an undercoat and a coating composition which mainly has a fluorine-containing copolymer having reactive sites for curing reactions, such as hydroxybutyl vinyl ether, glycidyl vinyl ether or the like be coated on the undercoat layer. However, though such a fluorine-containing copolymer is excellent in durability for the so-called paint resins, it hardly shows its water repellency at 110xc2x0 C. and above. The copolymer has another drawback, viz. when it is used to coat concrete or wood, it is difficult to retain the natural feel of the material and, when it is applied to cloths, their unique feel can hardly be preserved.
Concrete, wood, cloth and the like generally contain moisture and, for long-term use, the coating should be resistant or impervious to invasion of moisture from the outside of the coating as well. To solve this problem and workability-related problems, Japanese Kokai Publication Hei-02-52074 discloses a technology which uses a curing agent-free, noncrosslinking type fluorine-containing copolymer in a one component. However, this technology is still lacking in the ability to retain the natural feel of concrete or wood or the unique feel of cloths.
Japanese Kokai Publication Hei-02-107583 discloses a coating composition for cement-based concrete in which a water and oil repellent agent comprising a specific fluorine-containing silane compound is used and therefore which is excellent in weather resistance and stain resistance. From the viewpoint of long-term water repellent effect, however, this is still unsatisfactory.
Japanese Kokai Publication Hei-05-200353 discloses a technology according to which a coating composition comprising a hydroxyl- or carboxyl-containing fluoroolefin copolymer and a specific silane compound is used as a coating composition suited for application to cement-based substrates. However, while this technology attaches great importance to durability, it does not attend itself to water repellency.
International patent specification WO 95/18188 discloses a coating composition comprising a polyfluorinated carbon chain-containing compound and a silicone oil so that water and oil repellency and stain resistance may be acquired simultaneously. However, this composition has no effects in retaining the natural feel of concrete or wood or in retaining the unique feel of cloths.
Meanwhile, in recent years, acid rains associated with changes in the environment have become a serious problem and their influence on the human body and their erosive action on automotive body paint films and on the exterior walls and windowpanes of buildings and other structures, for instance, has been a serious concern. However, no effective means have so far been available against the problems caused by such acid rains.
In view of the current state of art mentioned above, it is an object of the present invention to provide a durable water repellent agent which can impart good water repellency to moisture-containing substrates such as concrete, wood, cloths, etc. and be expected to be effective against acid rain and which can maintain the natural material feel and unique feel of concrete, wood and cloths and can retain its water repellency for a prolonged period of time, and coated articles, in particular articles made of concrete, with said repellent composition applied thereto.
The durable water repellent agent of the present invention is a durable water repellent agent comprising a repellent and a fluorine-containing resin, and said repellent comprises at least one member selected from the group consisting of a perfluoroalkyl group-containing substance (I), a fluorine-containing surfactant (II), a fluorine-containing oil (III), a fluorosilicone oil (IV) and a silicone oil (V), the solid content weight ratio between said repellent and said fluorine-containing resin being (repellent):(fluorine-containing resin)=50:50 to 99:1.